In the prior art, in a lock for controlling a door of a safe, the body of the lock generally employs a straight-in/straight-out and square-shaped bolt or a wedge-shaped bolt. In a normal condition (locked-up condition), the bolt is restricted to be un-retracted, and it imposes a clog against a doorknob or door-release. In order to release the bolt from being restricted, a correct code should be input into the code entry device of the safe and be confirmed by a preset program in the device, and then an actuator assembly will act on to allow the lock to be unlocked. The bolt is reset to its normal condition (locked-up condition) by means of a return spring.
U.S. Pat. Nos. 5,142,890, 5,134,870 and 6,786,519 disclose several technical solutions of locks with swing bolts. In those solutions, a bolt is D-shaped (i.e., semicircular or a 180-degree sector), and a tension spring which is provided between the inside wall of a housing and the bolt is used as a return spring which forces the bolt from a turned-in position (unlocked position) to a turned-out position (locked-up position). The bolt can be locked up by a controllable solenoid, a head of an operating element (iron core) of the solenoid projects out and imposes directly a clog against a notch formed on the bolt.
In the above technical solutions, there are the following shortcomings.
If a lock is to be illegally and forcibly unlocked, a strong external force will be directly transferred to the bolt through the doorknob or door-release, and then the bolt will transfer the force to the head of the operating element (iron core) of the solenoid. A linear contact between the bolt and the head of the operating element will bring about a stress concentration, and this trends to cause some damage of both the operating element and the solenoid.
The D-shaped bolt is larger in dimension, the return spring mated to it, accordingly, requires a larger extension/retraction space. Because both of them occupy a larger space in the lock body, the volume available in the lock body becomes smaller and so it is very difficult to add other functional elements in the lock body.
Moreover, in the lock of the prior art for controlling a safe door, there exist the following problems with their actuator assembly. If a one-directional solenoid is used (returned by a spring), such a solenoid causes a larger power consumption, this is especially disadvantageous for a safe's lock which uses a dry battery for power supply; if a bi-directional solenoid is used, apart from complication, it requires a even larger mounting space.
In the designs that employ a motor and a mechanism which transforms a rotational movement into a linear movement as well as a screw-and-nut mechanism, because of being limited by a small space in the lock body, a small-sized high-speed motor is generally used, and so is a small-sized screw-and-nut mechanism. As such, in the case of rotating at a high speed, it is very difficult for the screw to engage with the nut exactly, which trends to cause a jam between the screw and the nut so as to further bring about damages of the screw-and-nut mechanism or the motor.